Power-driven hand tool



n t d a e P wfl POWER-DRIVEN HAND TOOL David R. Wickes, Detroit, Mich.

Application June 16, 1955, Serial No. 516,010 9 Claims. (Cl. 51-170)This invention relates to a power-driven hand tool of the rotating typesuch as a sander, buffer, grinder, etc.

It is an object of this invention to provide a hand tool of the abovedescribed type which is of economical construction and which is compact.

A further object of the invention is to provide a hand tool of the typedescribed in which the rotating work member such as the sanding disc,grinding wheel, bufling pad, etc. is designed to either rotateeccentrically about a fixed center or to both rotate about an eccentricand simultaneously revolve about its own axis.

In the drawing:

Fig. l is a side elevational view partly in section of a power-drivenhand tool of the present invention.

Fig. 2 is a sectional View along the lines 2-2 in Fig. l and showing thelocking member in the unlatched position.

Fig. 3 is a view similar to Fig. 2 and showing the lock ing member inthe latched position.

Fig. 4 is a sectional view along the lines .-4 in Fig. 2.

As indicated above, the hand tool of this invention may take the form ofa sander, grinder, buifer and the like. For the purpose of description,the hand tool is illustrated in the drawing as a sander; but it will beappreciated from the following description that the principle of theinvention may be applied to other power-driven hand tools.

The sander shown in the drawing comprises an airdriven motor having ahandle 12 and a finger-operated lever 14 for actuating a valve stem 16that controls the operation of motor 10. The rotor of motor 10 which isnot illustrated drives a shaft 18, and the shaft 18 in turn drives a pad20 against the lower face of which is supported a sanding disc 22. Pad20 and disc 22 form part of a pad assembly which includes a spindle 24,a locking screw 26 and a backing plate 28.

The present invention is directed primarily to the means by which thespindle 24 of the pad assembly is connected with the motor shaft 18.These means comprise a cylindrical driving head 30 having a socket 32extending axially therethrough at the center thereof. Socket 32 isdimensioned to receive the end of shaft 18, and two set screws 34 areprovided in head 30 for firmly locking the head 39 on the end of shaft18. Head 30 is also fashioned with a second socket 36. Socket 36 has itsaxis offset radially from the axis of socket 32 as shown clearly in Fig.4. Within socket 36, there is arranged a ball bearing 38. Bearing 38 hasan outer race 40 which is press fitted in socket 32. Spindle 24 has areduced upper end portion 42 which is press fitted into the inner race44 of bearing 38. Thus, with the arrangement described, spindle 24 isfree to rotate in bearing 38 and at the same time revolves with head 30about the axis of shaft 18.

For reasons described hereinafter, it is desirable at times to lockspindle 24 against rotation relative to head 30. Locking means are thusprovided to accomplish this. These means are preferably in the form of aring 46 which is pivotally supported on the lower face of head 30 as by2,794,303 Fatented June 4, 1957 a screw 48. As shown more clearly inFigs. 2 and 3, ring 'ice '- 46 is provided with a central aperture 50which surrounds spindle 24; and the inner periphery of ring 46 isprovided with a detent 52 engageable in a keyway 54 in spindle 24. Thearrangement is such that ring 46 can be pivoted in one direction aboutscrew 48 to interengage detent 52 in keyway 54 and thereby lock spindle24 relative to head 30 and may be pivoted in the opposite direction todisengage detent 52 from keyway 54 and thus permit spindle 24 to rotatefreely in head 3!).

In order to obtain smooth operation, I have found that it is necessaryto counterbalance head 3i) and thereby compensate for the eccennicmounting of the pad assembly on the head. This counterbalancing can beachieved most expeditiously by drilling holes such as indicated at 56 inthe upper face of head 30. The holes 56 are spaced and located such thatthe head 30 is perfectly balanced somewhere between the latched and theunlatched positions of the locking ring 46.

One of the important features of my construction resides in thealignment of shaft 18 with spindle 24. The

direction of rotation of the pad with locking ring 46 unlocked iscontrolled by inclining spindle 24 either toward or away from shaft 18.I have found that to obtain best results and more particularly, in orderto cause pad 20 to rotate in a direction opposite to the rotation ofhead 30,

' the axis of spindle 24 should be inclined in a downwardly directiontoward the axis of motorshaft 18. The extent of inclination, however,need not be very great; and I have found that when the axis of spindle24 is inclined towards the axis of shaft 18 even as little as 1, a verysatisfactory operation results. I have also found that as this angle ofinclination is increased, the rate of counter rotation of pad 20 is alsoincreased. An inclination of spindle 24 from about 1 to 5 is preferred.The tilting of spindle 24 relative to shaft 18 may be accomplished in avariety of different ways. Since this angle of inclination may be aslittle as 1", I have not attempted to show it on the drawings. Theinclination of spindle 24 may, for example, be provided by forming shaft18 with a slight taper or by forming the socket 32 with a slightlyenlarging taper in an inward direction. The necessary inclination mayalso be imparted to the spindle 24 by boring socket 32 or socket 36 atthe desired angle.

With the tool described above, I have found that a variety of difierentoperations can be performed. For example, when the tool is used as asander, its versatility enables its use for a variety of differentrequirements. With the spindle 24 locked to the head 39 as shown in Fig.3, the pad 20 and disc 22 rotate as a unit with head 30. In thiscondition, the sander is admirably suited for heavy stock removal; andyet, a fairly fine finish is obtained and the main objection of regulardisc sanders, namely, the formation of arcuate grooves, is eliminated.With the spindle locked to the head, the disc appears to produce acombined sanding and rubbing action. For example, a 4 disc with aneccentric mounting of /2" covers an area having a 5" diameter. Thisrubbing action while the disc is rotating tends to remove the swirls orgrooves which unavoidably result from a perfectly circular motion. Evenwith an average heavy paper, the sander in this condition can be usedfor relatively heavy stock removal and a fine mirror finish can beproduced. I have found also that with the spindle locked to the head,the heat produced is materially less than the heat encountered with aconventional sander where the sanding disc merely rotates about a fixedcenter. As a matter of fact, in this condition, the sander is admirablysuited for trimming the edges of plastic without causing burning of theplastic or the formation of a burr around the edge being trimmed orwithout producing objectionable heat on other materials.

However, if the locking ring 46 is pivoted to the unlatched conditionshown in Fig. 2, then the action of the pad 2% is entirely different. Inthis condition, with the motor it operating, when the pad 20 or disc 22.are brought to bear against a surface to be finished, I have found thatthe pad 29 rotates in a direction opposite to the direction of rotationof head 30. The cutting action is not as rapid as when the spindle islocked to the head; but on the other hand, a very fine finish isproduced without leaving swirls in the finished pattern as is commonwith orbital type sanders. This dual action, namely, the counterrotation of disc 22 together with its oscillating motion, is also verydesirable in that it has a tendency to unload the sanding disc 22; thatis, it tends to prevent the grit of the sanded material fromaccumulating on the disc. Experience has shown' that with a sanderconstructed in accordance with this invention, sanding discs last fromabout 50 to 70 percent longer than they do with conventional sanders.Furthermore, since the pad 20 and disc 22 rotate freely in bearing 38,there is no burning whatever. In addition, when the sander is operatingunder this dual action condition with the disc 22 lying fiat on thework, the torque on the handle which is experienced in conventionalsanders is substantially eliminated; and there is practically notendency for the sander to creep on the work.

Thus, depending on the type of work being finished and the type offinish produced, the user may operate the sander with the locking ring46 in either the latched or the unlatched condition to meet therequirements. For example, when working with sheet metal, if heavy stockremoval is required or if a mirror-bright surface is desired, the sanderis operated with the locking ring 46 in the latched position. On theother hand, if it is desired to put on a very fine matt or etch-likefinish on sheet metal, the sander is operated with the locking ring 46in the unlatched position.

Another advantage of the tool described herein resides in theconstruction of the driving head 30. It will be appreciated that byforming the head 36 as a cylindrical member provided with sockets 32 and36, a very economical coupling between the motor and the pad assembly isprovided. Furthermore, the head 30 is in and of itself a counterbalanceby reason of the bored holes 56.

I claim:

1. A portable disc sander or the like comprising a motor having ahousing and a driven shaft thereon, a head fixedly mounted at the freeend of said shaft, a work disc mounted on said head to rotate freelythereon relative to said housing about an axis which is offset radiallyfrom the axis of said motor shaft and means for optionally locking saiddisc to said head to cause the disc to rotate as a unit with said heador to rotate freely on'said head relative to said housing.

2. The combination called for in claim 1 wherein said last mentionedmeans comprises a ring member shiftably mounted on said head and havingmeans thereon for interengaging the work disc and the head for rotationas a unit when said ring member is shifted to one position on said head.

3. A portable disc sander or the like comprising a motor having aprojecting driven shaft, a work disc and means coupling said work discto said shaft comprising a generally cylindrical driving head fixed onthe end of said shaft to rotate therewith, said disc having a supportingspindle, means journalling said spindle for free rotation on said headabout an axis radially offset from the axis of said shaft, said spindleand said shaft projecting from opposite ends of said cylindrical drivinghead, said head having a ring member pivotally supported on the facethereof from which said spindle projects, said ring member encirclingsaid spindle and having means thereon for locking the spindle againstrotation on said head when the ring member is pivoted into engagementwith said spindle.

4. The combination called for in claim 3 wherein said spindle isprovided with a socket and said last mentioned means comprises a detenton said ring member engageable in said socket on the spindle. i i i 5. Aportable disc sander or the like comprising a motor having a housing anda driven shaft projecting therefrom, a work disc and means coupling saidwork disc to said shaft comprising a driving head, means fixedlyfmounting said driving head on the end of said shaft, said head having asocket therein the axis of which is radially offset from the axis ofsaid shaft, a bearing seated in said socket, said disc having asupporting spindle, said spindle being mounted in said hearing such thatthe spindle is journalled for free rotation on said head relative tosaid housing and means shiftably mounted on said head for movement to .aposition interengaging said spindle to thereby lock the spindle againstrotation on said head.

6. The combination called for in claim 5 wherein said spindle isprovided with a keyway and said last mentioned means comprises a detentengageable in said keyway.

7. A portable disc sander or the like comprising a motor having a drivenshaft, a head fixedly mounted at the free end of said shaft and a workdisc mounted on said head to rotate freely about an axis which is oifsetradially from and inclined slightly relative to the axis of said motorshaft.

8. The combination called for in claim 7 wherein said last mentionedaxis is inclined towards the axis of. the motor shaft at an angle fromabout 1 to 5".

' 9. A portable disc sander or the like comprising a motor having aprojecting driven shaft, a work disc and means coupling said work discto said shaft comprising a driving head, means fixedly mounting saiddriving head on the end of said shaft, said head having a socketthereinthe axis of which is radially offset from the axis of said shaft,a bearing seated in said socket, said disc having a supporting spindle,said spindle being mounted in said bearing such that the spindle isjournalled for free rotation on said head, the axis of said spindlebeing inclined slightly towards the axis of said shaft.

References Cited in the, file of this patent UNITED STATES PATENTS157,261 Wood Nov. 24, 1874 233,067 Buzzell Oct. 12, 1880 2,032,382Torrison Mar. 3, 1936 2,367,668 Champayne Jan. 23, 1945 2,706,875 HigleyApr. 26, 1955

